As a defensive back, the main mission statement of your football life is "Stop The Pass." If the ball is thrown to your receiver, it's your time to shine, and your priorities go in this order:
1. Intercept the ball.
2. Knock the ball down.
3. Make the tackle if the pass is caught.
Here's the right way to go for the knockdown.
Breaking Up The Pass
First and foremost, stay with your receiver, and do not let him get separation from you. He knows where the ball is, because he and the quarterback have worked this thing out ahead of time, so stay with him. Too many defensive backs start looking for the ball and lose their receiver in the process, which is a matter of technique, not skill. So, have your head on a swivel between your receiver and the quarterback. As the ball comes in, timing is critical. If you make contact before the ball gets there, you could be flagged for pass interference.
With your backside hand, secure the tackle in case you miss the ball. Put your front side hand in position like a bunt in baseball, don't swing at it. Most of the time if you swing at it, you'll miss. Once the ball is there, be as physical as you can be with the receiver. The more disruptions you can make to the normal throw and catch, the more likely it is that the receiver will drop the ball.
Breaking up a pass means an incompletion and loss of down for the opponent, which gets your offense one step closer to being back on the field. If you can't make the interception, using this technique will help you to cause the incompletion anyway.
